The present invention relates to covers or tarping systems for open-topped containers. The invention concerns an apparatus for pivotably mounting a flexible cover over the bed of a truck, such as a dump truck, and more specifically to an actuation mechanism for pivoting the cover over the truck bed.
Some hauling vehicles, such as dump trucks, include opentopped containers used for hauling or storing various materials. For example, in a typical dump truck application, the dump body is used to haul a variety of particulate material, such as gravel, aggregate or similar products. In addition, some hauling vehicles carry organic materials, such as grain or produce.
Depending upon the nature of the materials stored in the open-topped container, it is often desirable to provide a cover for the container. Of course, rigid covers are well known that may be hinged from one end of the container body. These rigid covers have gradually given way in the industry to flexible tarping systems because the flexible tarpaulin can be easily stowed when a cover is not necessary, such as when the dump bed is being loaded. Moreover, the flexible tarp is much easier to deploy than a rigid cover.
A variety of tarping systems have been developed that are geared to particular hauling vehicle applications. One such tarping system for use with dump trucks is the Easy Pull.RTM. Tarping System of Aero Industries, Inc. The Easy Pull.RTM. System includes a flexible tarp that is wound around a spool at one end of the dump bed. A rope attached to the free end of the tarp can be used to unwind the tarp from the roller to span the length of the dump bed.
Another cover system particular suited for open-topped containers on hauling vehicles, is the Easy Cover.RTM. Tarping System, also of Aero Industries, Inc. The Easy Cover.RTM. Tarping System includes a U-shaped bail that is pivotably mounted at its ends to the base of the container body. The horizontal section of the U-shaped bail is attached to the tarp, while the free ends of the vertical elements are pivotably mounted. In one application, the Easy Cover.RTM. Tarping System allows the tarp to be manually pulled in a sweeping arc over the container load.
In another application of the Easy Cover.RTM. System, an actuation mechanism is provided that automatically pivots the U-shaped bail member to deploy the tarp over the load within the open-topped container. When the actuation mechanism is released, it automatically pivots the bar, thereby unfurling the tarp from the tarp roller at the front of the vehicle. A hand crank or powered motor can be provided to rotate the tarp roller to wind the tarp when it is desired to open the container top. The hand crank or motor mechanism must be capable of providing sufficient mechanical advantage to overcome the deployment force of the actuation mechanism.
A vehicle 10 is depicted in FIG. 1 having an open-topped dumps body 13. As illustrated in FIG. 1, the vehicle can be a dump truck, with the open-topped container comprising a dump body. A tarpaulin cover 16 is shown in its deployed configuration spanning the length of the container and covering the load within. The tarp cover 16 can be wound onto a tarp roller 19. Both the tarp cover 16 and the roller 19 can be of a variety of known constructions, such as the Easy Cover.RTM. Tarping System.
A U-shaped bail member 22 is connected to one end of the tarp cover 16 in the manner described above. The bail member is pivotably mounted to the truck body 13 by way of an actuation mechanism 25. This actuation mechanism can take a variety of forms in the prior art. For instance, one such mechanism relies upon extension springs that apply a linear force at some point along the bail member 22, to cause the bail member to pivot when the tarp roller 19 is released. In a similar configuration, a compression spring is used to push the bail member outward, thereby pivoting it about its pivot mount at the base of the truck body 13.
In other applications, a coil torsion spring applies a torque or moment to the lower ends of the U-shaped bail member 22. One advantage of the coil torsion spring is that it can be mounted substantially under the truck body 13 so that the actuation mechanism is clear of the working area around the truck body. In some instances an under-body mount cannot be accomplished. In these instances, a spiral torsion spring assembly can be used to apply torque at the pivot mount of the bail member 22.
Once such spiral torsion spring of the prior art as depicted in FIGS. 2 and 3. In particular, the actuation mechanism 25' is mounted to the vehicle bed by a mounting plate 27. The actuation mechanism 25' includes a post 29 that projects from the mounting plate 27. The post is configured to extend through openings at the pivot mount for the bail member 22'. A torsion spring pack 31 is disposed within the pivot end 23' of the bail member 22'.
As shown most clearly in FIG. 3, the spring pack 31 can include a number of individual springs, such as torsion spring 31a. Each spring includes an anchor end 33 that is configured to fit within an anchor groove 35 defined along the length of the post 29. The opposite end of the torsion spring constitutes a reaction end 37 that reacts against a post 39 extending through the interior of the bail member 22'.
With any of the various actuation mechanisms described above, the amount of force generated by the mechanism depends upon the nature of the tarp cover 16 and the length that it must reach in its deployed position. Obviously, the longer the open-topped body 13, the longer distance the tarp cover 16 must cover. This translates to longer arms for the bail member 22. The longer the arms, the stronger the force or torque needed to pivot the arms from the stowed to the deployed position.
In order to generate this increased force using a spiral torsion spring configuration, such as that shown in FIGS. 2 and 3, additional springs, such as spring 31a, must be added to the spring pack 31. In one typical prior art spiral spring system, between three and six such springs are utilized, depending upon the length of the bail member arms. In the configuration depicted in FIG. 2, four such springs are provided. Each of the springs is aligned axially along the length of the post 29. Obviously, additional springs added to the pack 31 will require a longer post 29.
It has been found in practice that any spring pack using more than three springs projects too far from the side of the vehicle body 13. This excessive projection presents two problems: (1) since the arms of the bail member 22 necessarily project farther from the side of the body 13, they are more easily struck or damaged; and (2) federal law prohibits tarping system hardware from exceeding three inches from the side of the truck body. Since each spiral torsion spring is typically about one inch in width, it can be easily be appreciated that no more than three such springs can fit within the federally mandated envelope.
Consequently, there remains a need for an actuation mechanism that can utilize spiral torsion springs for a wide range of bail member dimensions, while still avoid the problems of the prior art system shown in FIGS. 2 and 3.